Mechanical joints for pressurized fluid handling tubing offer a large measure of convenience to the laboratory worker in that they may be easily assembled and disassembled in accordance with constantly changing system needs of the user. However, this convenience must be balanced with the possibility of leaks developing in the system at the joints. The invention described herein relates generally to an apparatus for simplifying mass spectrometer leak detector tests of these joints. More particularly, it relates to a rigid fitting which is snapped over a joint to be tested. It is a result of a contract with the Department of Energy.